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<title>BIO_f_base64</title>
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<ul id="index">
  <li><a href="#NAME">NAME</a></li>
  <li><a href="#SYNOPSIS">SYNOPSIS</a></li>
  <li><a href="#DESCRIPTION">DESCRIPTION</a></li>
  <li><a href="#NOTES">NOTES</a></li>
  <li><a href="#RETURN-VALUES">RETURN VALUES</a></li>
  <li><a href="#EXAMPLES">EXAMPLES</a></li>
  <li><a href="#BUGS">BUGS</a></li>
  <li><a href="#COPYRIGHT">COPYRIGHT</a></li>
</ul>

<h1 id="NAME">NAME</h1>

<p>BIO_f_base64 - base64 BIO filter</p>

<h1 id="SYNOPSIS">SYNOPSIS</h1>

<pre><code>#include &lt;openssl/bio.h&gt;
#include &lt;openssl/evp.h&gt;

const BIO_METHOD *BIO_f_base64(void);</code></pre>

<h1 id="DESCRIPTION">DESCRIPTION</h1>

<p>BIO_f_base64() returns the base64 BIO method. This is a filter BIO that base64 encodes any data written through it and decodes any data read through it.</p>

<p>Base64 BIOs do not support BIO_gets() or BIO_puts().</p>

<p>For writing, by default output is divided to lines of length 64 characters and there is a newline at the end of output. This behavior can be changed with <b>BIO_FLAGS_BASE64_NO_NL</b> flag.</p>

<p>For reading, first line should be at most 1024 bytes long including newline unless the flag <b>BIO_FLAGS_BASE64_NO_NL</b> is set. Further input lines can be of any length (i.e., newlines may appear anywhere in the input) and a newline at the end of input is not needed.</p>

<p>BIO_flush() on a base64 BIO that is being written through is used to signal that no more data is to be encoded: this is used to flush the final block through the BIO.</p>

<p>The flag <b>BIO_FLAGS_BASE64_NO_NL</b> can be set with BIO_set_flags(). For writing, it causes all data to be written on one line without newline at the end. For reading, it removes all expectations on newlines in the input data.</p>

<h1 id="NOTES">NOTES</h1>

<p>Because of the format of base64 encoding the end of the encoded block cannot always be reliably determined.</p>

<h1 id="RETURN-VALUES">RETURN VALUES</h1>

<p>BIO_f_base64() returns the base64 BIO method.</p>

<h1 id="EXAMPLES">EXAMPLES</h1>

<p>Base64 encode the string &quot;Hello World\n&quot; and write the result to standard output:</p>

<pre><code>BIO *bio, *b64;
char message[] = &quot;Hello World \n&quot;;

b64 = BIO_new(BIO_f_base64());
bio = BIO_new_fp(stdout, BIO_NOCLOSE);
BIO_push(b64, bio);
BIO_write(b64, message, strlen(message));
BIO_flush(b64);

BIO_free_all(b64);</code></pre>

<p>Read Base64 encoded data from standard input and write the decoded data to standard output:</p>

<pre><code>BIO *bio, *b64, *bio_out;
char inbuf[512];
int inlen;

b64 = BIO_new(BIO_f_base64());
bio = BIO_new_fp(stdin, BIO_NOCLOSE);
bio_out = BIO_new_fp(stdout, BIO_NOCLOSE);
BIO_push(b64, bio);
while ((inlen = BIO_read(b64, inbuf, 512)) &gt; 0)
    BIO_write(bio_out, inbuf, inlen);

BIO_flush(bio_out);
BIO_free_all(b64);</code></pre>

<h1 id="BUGS">BUGS</h1>

<p>On decoding, if the flag <b>BIO_FLAGS_BASE64_NO_NL</b> is not set and the first 1024 bytes of input do not include a newline character the first two lines of input are ignored.</p>

<p>The ambiguity of EOF in base64 encoded data can cause additional data following the base64 encoded block to be misinterpreted.</p>

<p>There should be some way of specifying a test that the BIO can perform to reliably determine EOF (for example a MIME boundary).</p>

<h1 id="COPYRIGHT">COPYRIGHT</h1>

<p>Copyright 2000-2024 The OpenSSL Project Authors. All Rights Reserved.</p>

<p>Licensed under the Apache License 2.0 (the &quot;License&quot;). You may not use this file except in compliance with the License. You can obtain a copy in the file LICENSE in the source distribution or at <a href="https://www.openssl.org/source/license.html">https://www.openssl.org/source/license.html</a>.</p>


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